Answer:
B. the distance around the circle
Explanation:
To easily answer this question, take a closer look at the given answer choices.
A says, "the length of the radius." Don't let the extra words trick you! This answer choice is just describing a radius. The term, "the length of--" is just there to trick you and to make you overthink. This answer choice is not correct because a radius =/= a circumference.
C says, "the length of the diameter." This is the exact same trick in choice A. Once you ignore the term, "the length off," you see that this answer choice is just describing a diameter. This answer is also incorrect because a diameter =/= a circumference.
D just says "270." This answer choice should not be considered, as there's no numbers involved in the question. The question is just looking for the definition of a circumference. Continually, not every circle's circumference is going to be 270. For these reasons, D is also an incorrect choice.
This leaves answer choice B. After eliminating the other answers, B becomes the remaining and correct choice. "The distance around the circle," is the only and correct definition of a circumference!